Identification and partial sequencing of a crocodile poxvirus associated with deeply penetrating skin lesions in farmed Nile crocodiles, Crocodylus niloticus.

When large numbers of crocodile skins were downgraded because of the presence of small pin prick-like holes, collapsed epidermal cysts were found deep in the dermis of juvenile crocodiles while forming cysts were observed in hatchlings. Histopathology of these forming cysts showed the presence of intracytoplasmic inclusions in proliferating and ballooning epidermal cells. Pox virions were seen in electron microscope preparations made from the scabs of such early lesions. The partial sequencing of virus material from scrapings of these lesions and comparison of it with the published sequence of crocodile poxvirus showed the virus associated with the deep lesions to be closely related, but different. To differentiate between the two forms of crocodile pox infection it is suggested that the previously known form should be called "classical crocodile pox" and the newly discovered form "atypical crocodile pox". The application of strict hygiene measures brought about a decline in the percentage of downgraded skins.

An outbreak of chlamydiosis in farmed Indopacific crocodiles (Crocodylus porosus).

An outbreak of chlamydiosis was diagnosed in hatchling and juvenile Indopacific crocodiles (Crocodylus porosus) on a crocodile farm in Papua New Guinea. The outbreak was characterised by high mortality with hepatitis and exudative conjunctivitis. The agent appears to have been introduced with live wild-caught crocodiles, which are purchased routinely by the farm. Improved quarantine procedures and treatment with tetracycline led to a rapid reduction of losses on the farm.

Morphology of the gular valve of the Nile crocodile, Crocodylus niloticus (Laurenti, 1768).

The morphology of the gular valve of the Nile crocodile was studied on the heads of eight 2.5-3-year-old commercially raised Nile crocodiles (Crocodylus niloticus). A description of the macroscopic and microscopic features of the gular valve is presented and the results are compared with published information on this species and other Crocodylia. The histological features are supplemented by information supplied by scanning electron microscopy (SEM). Anatomically, the dorsal and ventral components of the gular valve in the Nile crocodile form an efficient seal that effectively separates the oral and pharyngeal cavities consistent with the natural behavior and feeding habits of this animal. The gular valve is more complex in nature than superficial observations would suggest, with the dorsal and ventral folds being complemented by a series of smaller folds, particularly at the lateral fringes of the valve. Histologically, the surface epithelium of the valve demonstrates a transition from the typical stratified squamous epithelium of the oral cavity to that of the respiratory epithelium lining the pharyngeal cavity. The respiratory epithelium is characterized by the presence of ciliated cells and goblet cells and is accompanied by the appearance of large mucus-secreting glands in the underlying connective tissue. The transition between the two epithelial types is marked by the presence of a relatively prominent region where the stratified squamous epithelial cells undergo a gradual transformation into the typical elements of a respiratory epithelium. SEM graphically illustrated the extent of ciliation on both components of the gular valve as well as clearly defining the transition zones between the various types of surface epithelium present. No structures resembling taste receptors were observed in the mucosa of the gular valve.

In vitro cultivation of a south African isolate of an Anaplasma sp. in tick cell cultures.

This paper describes the first successful in vitro cultivation of a South African isolate of an Anaplasma sp., initially thought to be Anaplasma marginale, in the continuous tick cell line IDE8. Blood from a bovine naturally infected with A. marginale kept on the farm Kaalplaas (28 degrees 08' E, 25 degrees 38' S) was collected, frozen, thawed and used as inoculum on confluent IDE8 cell cultures. Twenty days after culture initiation small intracellular colonies were detected in a Cytospin smear prepared from culture supernatant. Cultures were passaged on Day 34. Attempts to infect IRE/CTVM18 cell cultures with the Kaalplaas isolate derived from IDE8 cultures failed, whereas a reference stock of A. marginale from Israel infected IRE/CTVM18 tick cell cultures. Attempts to infect various mammalian cell lines (BA 886, SBE 189, Vero, L 929, MDBK) and bovine erythrocytes, kept under various atmospheric conditions, with tick cell-derived Anaplasma sp. or the Israeli strain of A. marginale failed. Molecular characterization revealed that the blood inoculum used to initiate the culture contained both A. marginale and Anaplasma sp. (Omatienne) whereas the organisms from established cultures were only Anaplasma sp. (Omatjenne).

Caprine vertebral osteomyelitis caused by Rhodococcus equi.

There have been reports of Rhodococcus equi infections in goats in Australia, America and India. In this study, R. equi was isolated from an inflamed vertebra in a Boer goat in South Africa. At autopsy, there was a purulent inflammatory reaction in the 1st cervical vertebra. Histopathologically, a neutrophilic infiltration was encountered in the bone. Aerobic culture of swabs collected from the abscesses yielded R. equi in pure culture that was identified on biochemical tests. R. equi has become important as the cause of an opportunistic infection in people suffering from HIV.

Studies on the genus Setaria Viborg, 1795 in South Africa. III. Setaria thwaitei Mönnig, 1933.

Mönnig (1933) described Setaria thwaitei from a sable antelope, Hippotragus niger, the type host, as well as from roan antelope, Hippotragus equinus, and waterbuck, Kobus ellipsiprymnus. Yeh (1959) considered Setaria thwaitei to be synonym of Setaria hornbyi. Material collected from roan antelopes, sable antelopes and gemsbuck, Oryx gazella, from several localities in the north and south of South Africa, together with Mönnig's (1933) material, were re-examined. Measurements of the adult worms obtained in this study were compared with those in the original description of the species. Scanning electron microscopy of the anterior and posterior regions of the female worms confirmed S. thwaitei as a valid species.

General morphology of the oral cavity of the Nile crocodile, Crocodylus niloticus (Laurenti, 1768). II. The tongue.

The heads of nine 2.5 to 3-year-old Nile crocodiles (Crocodylus niloticus) were obtained from a commercial farm where crocodiles are raised for their skins and meat. The animals from which these specimens were obtained appeared clinically healthy at the time they were slaughtered. A description of the macroscopic and microscopic features of the tongue of the Nile crocodile is presented and the results are compared with published information on this species and other Crocodylia. The histological features are supplemented by information supplied by scanning electron microscopy. Macroscopic features of interest were the dome shaped structures grouped in a triangular formation on the posterior two-thirds of the dorsum of the tongue. These structures were identified by light microscopy to contain well-developed branched, coiled tubular glands and associated lymphoid tissue. Other histological features included a lightly keratinised stratified squamous surface epithelium supported by a thick layer of irregular dense fibrous connective tissue. Deep to this region was a clearly demarcated adipose tissue core with a dense mass of striated lingual musculature. Localised thickenings were present in the epithelium which were associated with ellipsoid intra-epithelial structures resembling taste buds.

General morphology of the oral cavity of the Nile crocodile, Crocodylus niloticus (Laurenti, 1768). I. Palate and gingivae.

The heads of nine 2.5 to 3-year-old Nile crocodiles (Crocodylus niloticus) were obtained from a commercial farm where crocodiles are raised for their skins and meat. The animals from which these specimens originated were clinically healthy at the time they were slaughtered. A detailed description of the macroscopic and microscopic features of the palate and gingivae of the Nile crocodile is presented and the results are compared with published information on this species and other Crocodylia. The histological features are supplemented by information supplied by scanning electron microscopy. Macroscopic features of interest are the small conical process situated at the base of the first two incisors of the maxilla, the distribution of cobbled units on the palate, and the broad dentary shelf forming the rostral aspect of the mandible. Histologically the palate and gingivae did not differ significantly from each other and both regions showed a presence of Pacinian-type corpuscles. Two types of sensory structures (taste receptors and pressure receptors) were identified in the regions examined, both involving modification of the epithelium and the underlying connective tissue.

Flowering in time: genes controlling photoperiodic flowering in Arabidopsis.

Successful sexual reproduction in plants relies upon the strict coordination of flowering time with favourable seasons of the year. One of the most important seasonal cues for the model plant Arabidopsis thaliana (Arabidopsis) is day length. Genes influencing flowering time in Arabidopsis have been isolated, some of which are involved in the perception and signalling of day length. This review discusses recent progress that has been made in understanding how Arabidopsis integrates environmental and internal signals to ensure a sharp transition to flowering and new insights on the role of the circadian clock in controlling the expression of genes that promote flowering in response to day length.

BIG: a calossin-like protein required for polar auxin transport in Arabidopsis.

Polar auxin transport is crucial for the regulation of auxin action and required for some light-regulated responses during plant development. We have found that two mutants of Arabidopsis-doc1, which displays altered expression of light-regulated genes, and tir3, known for its reduced auxin transport-have similar defects and define mutations in a single gene that we have renamed BIG. BIG is very similar to the Drosophila gene Calossin/Pushover, a member of a gene family also present in Caenorhabditis elegans and human genomes. The protein encoded by BIG is extraordinary in size, 560 kD, and contains several putative Zn-finger domains. Expression-profiling experiments indicate that altered expression of multiple light-regulated genes in doc1 mutants can be suppressed by elevated levels of auxin caused by overexpression of an auxin biosynthetic gene, suggesting that normal auxin distribution is required to maintain low-level expression of these genes in the dark. Double mutants of tir3 with the auxin mutants pin1, pid, and axr1 display severe defects in auxin-dependent growth of the inflorescence. Chemical inhibitors of auxin transport change the intracellular localization of the auxin efflux carrier PIN1 in doc1/tir3 mutants, supporting the idea that BIG is required for normal auxin efflux.

Determination of the relative expression levels of rubisco small subunit genes in Arabidopsis by rapid amplification of cDNA ends.

Multigene families are common in higher organisms. However, due to the close similarities between members, it is often difficult to assess the individual contribution of each gene to the overall expression of the family. In Arabidopsis thaliana, there are four genes encoding the small subunits (SSU) of ribulose-1.5-bisphosphate carboxylase oxygenase (rubisco) whose nucleotide sequences are up to 98.4% identical. In order to overcome the technical limitations associated with gene-specific probes (or primers) commonly used in existing methods, we developed a new gene expression assay based on the RACE (rapid amplification of cDNA ends) technique with a single pair of primers. With this RACE gene expression assay, we were able to determine the relative transcript levels between four Arabidopsis SSU genes. We found that the relative SSU gene expression differed significantly between plants grown at different temperatures. Our observation raises the possibility that an adaptation of rubisco to the environment may be achieved through the specific synthesis of the SSU proteins, which is determined by the relative expression levels between the SSU genes.

Analysis of the function of two circadian-regulated CONSTANS-LIKE genes.

The Arabidopsis genes CONSTANS-LIKE 1 (COL1) and CONSTANS-LIKE 2 (COL2) are predicted to encode zinc finger proteins with approximately 67% amino acid identity to the protein encoded by the flowering-time gene CONSTANS (CO). We show that the circadian clock regulates expression of COL1 and COL2 with a peak in transcript levels around dawn. We analyzed transgenic plants misexpressing COL1, COL2 and CO. Unlike CO, altered expression of COL1 and COL2 in transgenic plants had little effect on flowering time. However, analysis of circadian phenotypes in the transgenic plants showed that over-expression of COL1 can shorten the period of two distinct circadian rhythms. Experiments with the highest COL1 over-expressing line indicate that its circadian defects are fluence rate-dependent, suggesting an effect on a light input pathway(s).

Functional importance of conserved domains in the flowering-time gene CONSTANS demonstrated by analysis of mutant alleles and transgenic plants.

CONSTANS promotes flowering of Arabidopsis in response to long-day conditions. We show that CONSTANS is a member of an Arabidopsis gene family that comprises 16 other members. The CO-Like proteins encoded by these genes contain two segments of homology: a zinc finger containing region near their amino terminus and a CCT (CO, CO-Like, TOC1) domain near their carboxy terminus. Analysis of seven classical co mutant alleles demonstrated that the mutations all occur within either the zinc finger region or the CCT domain, confirming that the two regions of homology are important for CO function. The zinc fingers are most similar to those of B-boxes, which act as protein-protein interaction domains in several transcription factors described in animals. Segments of CO protein containing the CCT domain localize GFP to the nucleus, but one mutation that affects the CCT domain delays flowering without affecting the nuclear localization function, suggesting that this domain has additional functions. All eight co alleles, including one recovered by pollen irradiation in which DNA encoding both B-boxes is deleted, are shown to be semidominant. This dominance appears to be largely due to a reduction in CO dosage in the heterozygous plants. However, some alleles may also actively delay flowering, because overexpression from the CaMV 35S promoter of the co-3 allele, that has a mutation in the second B-box, delayed flowering of wild-type plants. The significance of these observations for the role of CO in the control of flowering time is discussed.

Oribatid mites (Acari, Oribatida) as intermediate hosts of tapeworms of the Family Anoplocephalidae (Cestoda) and the transmission of Moniezia expansa cysticercoids in South Africa.

Six species of adult oribatid mites (Galumna racilis, Kilimabates pilosus, Kilimabates sp., Scheloribates fusifer, Muliercula ngoyensis and Zygoribatula undulata) and two immature stages belonging to the superfamilies Galumnoidea and Ceratozetoidea were isolated from a lawn (mixed Pennisetum and Cynodon spp.) at Onderstepoort Veterinary Institute, South Africa. The mites were subsequently used in an infection trial using Moniezia expansa eggs. Tapeworm cysticercoids were recovered in G. racilis, K. pilosus, Kilimabates sp., S. fusifer, M. ngoyensis and Z. undulata, as well as in immatures of Ceratozetoidea. The percentage of infected mites was 7,6, 6,3, 16,4, 66,7, 57,1, 60,0 and 46,7% respectively. Immatures of Galumnoidea did not become infected. The highest number of cysticercoids isolated from one individual was six from an adult S. fusifer.

MDH1: an apple homeobox gene belonging to the BEL1 family.

Differential display was used to isolate genes differentially expressed early in fruit development of apple (Malus domestica Borkh.). This approach resulted in the isolation of MDH1, a homeobox gene with a homeodomain similar to that of BELL1 (BEL1), which is involved in regulation of ovule development in Arabidopsis. However, outside the homeodomain MDH1 is quite different from BEL1. In apple, MDH1 mRNA was predominantly found in flowers, expanding leaves and expanding fruit. In pre-anthesis flowers, in situ hybridization showed that MDH1 mRNA accumulated in ovules. To further investigate the function of this new homeobox gene, MDH1 was transformed into Arabidopsis thaliana under the control of the cauliflower mosaic virus 35S promoter. The transgenic Arabidopsis plants showed dwarfing, reduced fertility and changes in carpel and fruit (silique) shape. The size and shape of the cells in the transgenic fruit was irregular. Both the transgenic phenotypes in Arabidopsis and the expression pattern of this gene in apple are consistent with the idea that MDH1 is likely to play an important role in control of plant fertility.

Studies on the genus Setaria Viborg, 1795 in South Africa. I. Setaria africana (Yeh, 1959).

Setaria africana (Yeh, 1959) is represented by two subspecies, Setaria africana africana Troncy, Graber & Thal, 1976 from giant eland (Taurotragus derbianus) from the Central African Republic and Cameroon and Setaria africana farchai Troncy, Graber & Thal, 1976 from bushbuck (Tragelaphus scriptus), also from the Central African Republic. Material collected from nyala (Tragelaphus angasii), bushbuck and kudu (Tragelaphus strepsiceros) from several localities in the eastern region of South Africa was re-examined. Measurements of adult worms confirmed the differences between the two subspecies and scanning electron microscopy showed that the deirids of S. africana africana are single whereas those of S. africana farchaiare double. Setaria africana farchaiis recorded for the first time in South Africa.

GIGANTEA: a circadian clock-controlled gene that regulates photoperiodic flowering in Arabidopsis and encodes a protein with several possible membrane-spanning domains.

Flowering of Arabidopsis is promoted by long days and delayed by short days. Mutations in the GIGANTEA (GI) gene delay flowering under long days but have little or no effect under short days. We have now isolated the GI gene and show that it encodes a novel, putative membrane protein. By comparing the sequence of the Arabidopsis gene with that of a likely rice orthologue and by sequencing mutant alleles, we identify regions of the GI protein that are likely to be important for its function. We show that GI expression is regulated by the circadian clock with a peak in transcript levels 8-10 h after dawn. The timing, height and duration of this peak are influenced by daylength. We analysed the interactions between GI and the LHY, CCA1 and ELF3 genes, previously shown to affect daylength responses; we show that the rhythmic pattern of GI expression is altered in the elf3, CCA1-OX and lhy genotypes, and that CCA1 and LHY expression are reduced by gi mutations. Our results are consistent with the idea that GI plays an important role in regulating the expression of flowering time genes during the promotion of flowering by photoperiod.

Molecular genetics of gynoecium development in Arabidopsis.

Carpels are the ovule-bearing structural units in angiosperms. In Arabidopsis, the specification of carpel identity is achieved by at least two separate pathways: a pathway mediated by the C class gene AG and an AG-independent pathway. Both pathways are negatively regulated by A class genes. Two genes, SPT and CRC, can promote differentiation of carpel tissue independently of AG and are thus components of the AG-independent pathway. CRC and SPT appear to act in a redundant manner to promote the differentiation of subsets of carpel tissues. The carpel primordium is subdivided into regional domains, both medial versus lateral and abaxial versus adaxial. Based on morphological and gene expression analyses, it appears likely that these domains define developmental compartments. The medial domain appears fated to differentiate into the marginal tissue types of the carpel (septum with transmitting tract and placenta with ovules), whereas the lateral domain gives rise to the ovary walls. The expression of ETT defines the abaxial domain, and this gene is involved in the abaxial-adaxial and, possibly, the apical-basal patterning of tissues in the carpel. Once regional domains have been established, the differentiation of tissue and cell types occurs. The MADS-box gene FUL and AGLI/5 are involved in the differentiation of specific tissue types in the valves and valve margins. Thus, the genes identified can be arranged in a functional hierarchy: specification of carpel identity, patterning of the carpel primordium and directing the differentiation of the specialized tissues of the carpel.

Identification of genes expressed during early Arabidopsis carpel development by mRNA differential display: characterisation of ATCEL2, a novel endo-1,4-beta-D-glucanase gene.

The floral homeotic gene AGAMOUS (AG) imparts carpel identity on the fourth whorl of floral organs in wild-type Arabidopsis flowers. Less is known about the genes that regulate carpel patterning and differentiation. To identify cndidate regulators, we screened for genes expressed in developing carpels. Since Arabidopsis carpels are difficult to isolate, we used whole inflorescence apices of two floral homeotic mutants (pi and pi ag) and mRNA differential display, to identify carpel transcripts. Two of the resulting cDNA clones were shown to be expressed predominantly in flowers. They encoded AGL11, a MADS box transcription factor known to be expressed in the carpel and ovules, and a novel Arabidopsis endo-1,4-beta-D-glucanase (ATCEL2). In situ hybridisation localised the ATCEL2 transcript to the developing septum and ovule primordia of young carpels.